Large differences in ammonia emission factors between greenhouse and open-field systems under different practices across Chinese vegetable cultivation.

Estimating ammonia (NH3) emission factors (EFs) for vegetable production can support assessment of potential atmospheric pollution risk and provide information for mitigating NH3 volatilization. The EFs in greenhouse and open-field systems under different fertilization, irrigation regimes, vegetable types and soil properties in both greenhouse and open-field vegetable production systems in China are poorly understood. An integrated analysis was performed, including 282 field measurements of NH3 volatilization from 54 field studies, to quantify ammonia EFs under different management practices and soil properties. The results showed that the mean ammonia EF across all measurements was 4.2 % (3.6 %-4.8 %). The EFs of greenhouse and open-field systems were 2.0 % (1.5 %-2.5 %) and 6.3 % (5.4 %-7.2 %), respectively. There was a power function relationship between nitrogen application rate and ammonia EF in greenhouses. No relationship was identified between nitrogen application rate and ammonia EF in the open-field system. The EFs of organic fertilizers were lower than those of both chemical fertilizers and the combination of chemical and organic fertilizers. EFs of leafy vegetables, cabbages, solanaceous vegetables and melons were 2.7 %, 2.9 %, 1.4 % and 1.4 % in the greenhouse system, and 5.2 %, 5.7 %, 7.6 % and 9.7 % in the open-field system, respectively. The EFs of the greenhouse production system increased with increasing soil organic matter. Boosted regression tree analysis showed that N application rate, pH and soil organic matter were the main driving factors of EFs in the greenhouse system. Vegetable type, pH and soil organic matter were the main driving factors in the open-field system. In this study, the EFs were evaluated and distinguished across greenhouse and open-field systems, and the results provided accurate EFs under different management practices and soil properties for vegetable production in both greenhouse and open-field systems.

Clamping-force induced birefringence in a single-mode fiber in commercial V-grooves investigated with distributed polarization analysis: erratum.

We correct several errors in our publication [Opt. Express30(4): 5347 (2022)10.1364/OE.452756].

Clamping-force induced birefringence in a single-mode fiber in commercial V-grooves investigated with distributed polarization analysis.

V-grooves are critical components for attaching fiber pigtails to photonics integrated circuits and for holding fibers in optical devices. Improper choice of V-groove angles and clamping method may cause large birefringence in the fibers and degrade polarization related performance of the devices. In this paper, we theoretically analyze the clamping-force induced birefringence of a single-mode (SM) fiber clamped in a V-groove by a flat-lid or by two identical V-grooves, respectively. We build a distributed polarization analyzer with complete Muller matrix analysis capability, which enables us to accurately measure local birefringence values in the fiber induced by clamped V-grooves of different angles. We find that for a SM fiber clamped in a commercial V-groove made with ZrO2 or SiO2 by a flat-lid, the zero-birefringence (ZB) angle is almost exactly 60°, suggesting that the friction coefficient in the V-groove can be safely ignored. In contrast, previous studies either indicated that the ZB V-groove angles clamped by a flat-lid never existed or significantly deviated from 60° due to the friction coefficient. More importantly, we also find, for the first time, both theoretically and experimentally, that a SM fiber clamped by two identical commercial V-grooves has a ZB when the V-groove angle is 90°. The methods and results reported in this paper shall prove beneficial for the fiber optic component industry to optimize polarization related performances of devices for sensing, communication, and instrumentation applications.